1. Field of the Invention
The present invention relates to a recording apparatus and a method for judging the recording state of such a recording apparatus.
2. Related Background Art
In an ink jet recording apparatus such as a recording apparatus which uses a recording head (hereinafter referred to as "head") wherein ink is discharged by causing the change of state of ink with thermal energy, for example, there has hitherto been proposed a method whereby to detect the presence of ink in the head as given below.
In other words, means for detecting the head temperature is provided to detect by this temperature detecting means the difference in temperature before the heater of the head is heated and after it has been heated. If the temperature difference is smaller than a given value, it is judged that the ink is present. On the contrary, if such a difference is greater than the given value, it is judged that the ink is absent. This detection utilizes the thermal capacity of the head which is greater when ink is present and is smaller when it is absent.
Also, as another method, a pressure sensor is provided in the ink supply passage. It is judged that the ink is present if the value of this pressure sensor is greater than a given value, and that no ink is present if the value is lower than the given one.
Further, various methods are designed by means of detecting the weight of an ink cartridge, the electrical resistance and electrical capacitance of the ink, or the application of an optical sensor to detect the transmission of light among others.
With any one of these methods, it is possible to judge the presence of ink in the ink cartridge of the head or the state where the ink is supplied to the head.
Nevertheless, there are the drawbacks given below in the above-mentioned ink jet recording apparatus.
An ink let recording apparatus has a fundamental weak point in that it sometimes results in a disabled ink discharge due to the clogging of its nozzles when the ink is dried or air bubbles are generated in the nozzles. This phenomenon may take place at the very beginning of recording or in the course of recording.
In order to overcome this weak point, various measures have been taken. So far the best measure has been taken for the recovery operation when any clogging occurs, but no perfect measure taken has been effecting yet to prevent clogging from occurring. Therefore, even when it is judged that the ink is present by means to detect the presence of ink, there may be some case where the phenomenon of the disabled recording is encountered if a clogging occurs.
In a case where an ink let recording apparatus is used as a facsimile recording apparatus, no image is recorded on a recording sheet at all or the image disappears in the middle of a page if the above-mentioned clogging occurs even when the receiving is conducted for recording with the judgement that the ink is present as well as the confirmation that the receiving has been completed is communicated to the transmitting side. In this case, a serious error may result: the transmitting side considers that the communication has been completed normally and a message or original has been transmitted as desired despite the fact that the recording has not been executed normally on the receiving side.
In other words, the conventional method is not good enough to accurately detect whether a facsimile reception recording has been normally executed.